1. Field of the Invention
The present invention relates to a toroidal-type continuously variable transmission and a continuously variable transmission apparatus which can be used as a transmission unit constituting an automatic transmission apparatus for a vehicle or a transmission for controlling the operating speed of various industrial machines such as a pump.
2. Description of the Related Art
It is has been studied to use such a toroidal-type continuously variable transmission as shown in FIGS. 8 and 9 as a transmission for a vehicle, and such use of the toroidal-type continuously variable transmission has been enforced in part of the vehicle industry. In this toroidal-type continuously variable transmission, for example, as disclosed in JP-62-71465U, an input side disk 2 is supported concentrically with an input shaft 1 and an output side disk 4 is fixed to the end portion of an output shaft 3 disposed concentrically with the input shaft 1. Inside a casing 5 (see FIG. 11 which will be discussed later) in which the toroidal-type continuously variable transmission is stored, there are disposed trunnions 7, 7 which can be swung about pivot shafts 6, 6 disposed at positions twisted with respect to the input shaft 1 and output shaft 3.
Specifically, a pair of pivot shafts 6, 6 are disposed on the outer surfaces of the two end portions of each of the trunnions 7 in such a manner that the two pivot shafts 6, 6 are concentric with each other. The center axes of the pivot shafts 6, 6 do not intersect with the center axes of the input side and output side disks 2, 4 but are present at twisted positions which exist in directions almost at right angles to the directions of the center axes of the input side and output side disks 2, 4. Also, on the central portions of the respective trunnions 7, 7, there are supported the base half sections of displacement shafts 8, 8. In case where the trunnions 7, 7 are respectively swung about their associated pivot shafts 6, 6, the inclination angles of the displacement shafts 8, 8 can be adjusted. On the peripheries of the front half sections of the displacement shafts 8, 8 supported on the trunnions 7, 7, there are supported power rollers 9, 9 in such a manner that they can be rotated. And, the power rollers 9, 9 are held by and between the inner surfaces 2a, 4a of the input side and output side disks 2, 4.
The sections of the mutually opposing inner surfaces 2a, 4a of the input side and output side disks 2, 4 are respectively formed in a concave surface having an arc-shaped section, while the concave surface can be obtained by rotating an arc having the pivot shaft 6 as a center thereof or by rotating a curved line close to such arc. And, the peripheral surfaces 9a, 9a of the power rollers 9, 9 each formed in a spherically convex surface are respectively contacted with the inner surfaces 2a, 4a of the input side and output side disks 2, 4. Also, between the input shaft 1 and input side disk 2, there is interposed a loading cam device 10. The input side disk 2 can be rotated by the loading cam device 10 while it is elastically pressed toward the output side 4 by the cam loading device 10
When the above-structured toroidal-type continuously variable transmission is in use, as the input shaft 1 is rotated, the loading cam device 10 rotates the input side disk 2 while pressing the input side disk 2 against the plurality of power rollers 9, 9. And, the rotational movement of the input side disk 2 is transmitted through the plurality of power rollers 9, 9 to the output side disk 4, so that the output shaft 3 fixed to the output side disk 4 can be rotated.
When changing the rotation speed between the input shaft 1 and output shaft 3, firstly, to reduce the rotation speed between the input shaft 1 and output shaft 3, the trunnions 7, 7 may be swung about the pivot shafts 6, 6 and the displacement shaft 8, 8 may be inclined in such a manner that the peripheral surfaces 9a, 9a of the power rollers 9, 9, as shown in FIG. 8, can be respectively contacted with the near-to-center portion of the inner surface 2a of the input side disk 2 and the near-to-outer-periphery portion of the inner surface 4a of the output side disk 4.
On the other hand, to increase the rotation speed between the input shaft 1 and output shaft 3, the trunnions 7, 7 may be swung and the displacement shaft 8, 8 may be inclined in such a manner that the peripheral surfaces 9a, 9a of the power rollers 9, 9, as shown in FIG. 9, can be respectively contacted with the near-to-outer-periphery portion of the inner surface 2a of the input side disk 2 and the near-to-center portion of the inner surface 4a of the output side disk 4. In case where the inclination angles of the displacement shafts 8, 8 are set intermediate between FIGS. 8 and 9, an intermediate transmission ratio can be obtained between the input shaft 1 and output shaft 3.
Further, FIGS. 10 and 11 show a more specified toroidal-type continuously variable transmission which is disclosed in JP-A-1-173552U. In this toroidal-type continuously variable transmission, an input side disk 2 and an output side disk 4 are respectively supported on the periphery of a circular-pipe-shaped input shaft 11 in such a manner that they can be rotated. Also, between the end portion of the input shaft 11 and input side disk 2, there is interposed a loading cam device 10. On the other hand, an output gear 12 is coupled to the output side disk 4 in such a manner that the output side disk 4 and output gear 12 can be rotated synchronously.
Pivot shafts 6, 6, which are disposed on the two end portions of each of a pair of trunnions 7, 7 in such a manner that the pivots 6, 6 are concentric with each other, are supported on their associated pair of support plates 13, 13 in such a manner that they can be swung as well as can be displaced in the axial direction thereof (that is, in FIG. 10, in the front and back direction of the figure sheet; and, in FIG. 11, in the right and left direction). And, on the intermediate portions of the respective trunnions 7, 7, there are supported the base half sections of the displacement shafts 8, 8. Each of the displacement shafts 8, 8 is structured such that the base halt section thereof and the front half section thereof are eccentric to each other. And, the base half sections of the displacement shafts 8, 8 are rotatably supported on the intermediate portions of their associated trunnions 7, 7, while the power rollers 9, 9 are rotatably supported on the front half sections of the displacement shafts 8, 8.
By the way, the pair of displacement shafts 8, 8 are disposed at positions 180° opposite to the input shaft 11. Also, the eccentric direction between the base half sections and front half sections of the displacement shafts 8, 8 is the same direction (in FIG. 11, the reversed right and left direction) with respect to the rotation direction of the input side and output side disks 2, 4. Further, the eccentric direction is a direction extending almost at right angles to the arrangement direction of the input shaft 11. Therefore, the power rollers 9, 9 are supported in such a manner that they can be displaced slightly with respect to the arrangement direction of the input shaft 11.
Also, between the outer surfaces of the power rollers 9, 9 and the inner surfaces of the intermediate portions of the trunnions 7, 7, there are disposed thrust ball bearings 14, 14 and thrust needle roller bearings 15, 15 in the order starting from the outer surfaces of the power rollers 9, 9. The thrust ball bearings 14, 14, while supporting thrust-direction loads applied to the power rollers 9, 9, allow the power roller 9, 9 to rotate. Also, the thrust needle roller bearings 15, 15, while supporting thrust loads applied from the power rollers 9, 9 to outer races 16, 16 forming the thrust ball bearings 14, 14, allow the front half sections of the displacement shafts 8, 8 and the outer races 16, 16 to be swung about the base half sections of the displacement shafts 8, 8. Further, the trunnions 7, 7 can be displaced in the axial direction thereof by actuators 17, 17 each of an oil pressure type.
In the case of the above-structured toroidal-type continuously variable transmission, the rotational movement of the input shaft 11 is transmitted through the loading cam device 10 to the input side disk 2. And, the rotational movement of the input side disk 2 is transmitted through a pair of power rollers 9, 9 to the output side disk 4 and further the rotational movement of the output side disk 4 is taken out by the output gear 12.
To change the rotation speed ratio between the input shaft 11 and output gear 12, the pair of trunnions 7, 7 maybe respectively displaced in the mutually opposite directions by their associated actuators 17, 17; for example, the power roller 9 shown on the lower side in FIG. 11 is displaced to the right in FIG. 11, whereas the power roller 9 shown on the upper side in FIG. 11 is displaced to the left in FIG. 11. This changes the direction of a tangential-direction force acting on the contact portions between the peripheral surfaces 9a, 9a of the power rollers 9, 9 and the inner surfaces 2a, 4a of the input side and output side disks 2, 4. And, due to such change in the direction of the tangential-direction force, the trunnions 7, 7 are swung in the mutually opposite directions about the pivot shafts 6, 6 which are pivotally supported on the support plates 13, 13. As a result of this, as shown in FIGS. 8 and 9 which have been previously discussed, the contact positions between the peripheral surfaces 9a, 9a of the power rollers 9, 9 and the inner surfaces 2a, 4a of the input side and output side disks 2, 4 are changed, thereby changing the rotation speed ratio between the input shaft 11 and output gear 12.
When transmitting the power by the toroidal-type continuously variable transmission, the power rollers 9, 9 are displaced in the axial direction of the input shaft 11 in accordance with the elastic deformation of the respective composing parts of the toroidal-type continuously variable transmission. And, the displacement shafts 8, 8 supporting the power rollers 9, 9 are slightly rotated about their respective base half sections. This slight rotation displaces the outer surfaces of the outer races 16, 16 of the thrust ball bearings 14, 14 and the inner surfaces of the trunnions 7, 7 with respect to each other. Between these outer and inner surfaces, there are interposed the thrust needle roller bearings 15, 15 and, therefore, such relative shift can be attained with a small force.
In the case of the above-structured toroidal-type continuously variable transmission, power transmission between the input shaft 11 and output gear 12 is carried out by the two power rollers 9, 9. Therefore, the-power per unit area to be transmitted between the peripheral surfaces 9a, 9a of the power rollers 9, 9 and the inner surfaces 2a, 4a of the input side and output side disks 2, 4 increases, which generates a limit on the power that can be transmitted. In view of this, in order to be able to increase the power that can be transmitted by the toroidal-type continuously variable transmission, in related art, it has also been proposed to increase the number of power rollers 9, 9.
As a first example of a structure for increasing the number of power rollers 9, 9 to accomplish the above purpose, in related art, there is known a structure in which, as disclosed in JP-A-3-74667, between a set of input side disk 2 and output side disk 4, there are interposed three power rollers 9, 9 and power is transmitted between the set of input side disk 2 and output side disk 4 by the three power rollers 9, 9. In the case of the structure disclosed in this publication, as shown in FIG. 12, at the three positions of a fixed frame 18 that are arranged at regular intervals in the circumferential direction of the fixed frame 18, there are pivotally supported the respective middle portions of three support pieces 19, 19 each of which is bent at an angle of 120°. And, between the mutually adjoining support pieces 19, 19, there are supported three trunnions 7, 7 in such a manner that they can be swung and can be displaced in the axial direction thereof.
Each of the three trunnions 7, 7 includes on the two end portions thereof two pivot shafts 6 which are concentric with each other. The trunnions 7, 7 can be displaced in the axial direction of their respective pivot shafts 6 by their respective actuators 17, 17 each of an oil pressure type. Three oil pressure cylinders 20, 20, which respectively constitute their associated actuators 17, 17, communicate through a control valve 21 with the jet-out opening of a pump 22 serving as an oil pressure source. This control vale 21 includes a sleeve 23 and a spool 24 which can be respectively displaced in the axial direction thereof (in FIG. 12, in the right and left direction).
To change the inclination angles of the power rollers 9, 9 respectively pivotally supported on their associated trunnions 7, 7 by their associated displacement shafts 8, 8, the sleeve 23 may be displaced in the axial direction thereof (in FIG. 12, in the right and left direction) by a control motor 25. Due to this, pressure oil jetted out from the pump 22 is supplied through pressure oil pipes into the respective oil pressure cylinders 20, 20. And, drive pistons 26, 26, which are respectively fitted into their associated oil pressure cylinders 20, 20 and are used to shift their associated trunnions 7, 7 in the axial direction of their respective pivot shafts, are displaced in the same directions with respect to the rotation direction of the input side and output side disks 2 and 4 (see FIGS. 8 and 9). Also, operation oil, which has been pushed out from the respective oil pressure cylinders 20, 20 with the displacement movements of the respective drive pistons 26, 26, is returned to an oil tank 27 through an oil pressure pipe (part of which is not shown) including the control valve 21.
On the other hand, the displacement movements of the respective drive pistons 26, 26 caused by the supply of the pressure oil are transmitted to the spool 24 through a precess cam 28 and a link 29, thereby displacing the spool 24 in the axial direction thereof. As a result of this, in a state where the drive piston 26 is displaced by a given amount, the flow passage of the control valve 21 is closed to thereby stop the supply and discharge of the pressure oil with respect to the oil pressure cylinders 20, 20. Therefore, the displacement amounts of the respective trunnions 7, 7 in the axial direction thereof can be set so as to correspond to the displacement amount of the sleeve 23 provided by the control motor 25.
Further, in order to be able to increase the power that can be transmitted by a toroidal-type continuously variable transmission, as a second example of a structure for increasing the number of power rollers 9, 9 to achieve the above purpose, in related art, there is also known a structure of a so called double-cavity type in which, as shown in FIG. 13, input side disks 2A, 2B and output side disks 4, 4 are disposed by twos on the periphery of an input shaft 11a and also these input side disks 2A, 2B and output side disks 4, 4 are arranged in parallel to each other in the power transmission direction. In the structure shown in FIG. 13, an output gear 12a is supported on the periphery of the middle portion of the input shaft 11a in such a manner that it can be rotated with respect to the input shaft 11a, while the output side disks 4, 4 are spline engaged with the two end portions of a cylindrical portion disposed in the central portion of the output gear 12a. Also, the input side disks 2A, 2B are supported on the two end portions of the input shaft 11a in such a manner that they can be rotated together with the input shaft 11a. The input shaft 11a can be driven or rotated by a drive shaft 100 through a loading cam device 10. In the case of the thus structured toroidal-type continuously variable transmission of a double cavity type, the power transmission from the input shaft 11a to the output gear 12a can be carried out through the following two routes; that is, one route between one input side disk 2A and one output side disk 4, the other between the other input side disk 2B and the other output side disk 4. Therefore, in this case, transmission of large power can be realized.
When incorporating the above structured toroidal-type continuously variable transmission into an actual continuously variable transmission for a vehicle, in related art, as disclosed in JP-A-1-169169, JP-A-1312266, JP-A-10-196759 and JP-A-11-63146, there is proposed an idea of combining the toroidal-type continuously variable transmission with a planetary gear mechanism. That is, in the low speed running operation of the vehicle, the drive power of an engine is transmitted only by the toroidal-type continuously variable transmission and, in the high speed running operation, the drive power is transmitted by the planetary gear mechanism, thereby reducing the torque that is applied to the toroidal-type, continuously variable transmission in the high speed running operation. To structure the toroidal-type continuously variable transmission in this manner can enhance the durability of the respective composing parts of the present toroidal-type continuously variable transmission.
Now, FIG. 14 shows a continuously variable transmission apparatus which is disclosed in the above cited JP-A-11-63146. This continuously variable transmission apparatus is composed of a combination of a toroidal-type continuously variable transmission 30 of a double cavity type and a planetary gear mechanism 31. And, in the low speed running operation of the vehicle, power is transmitted only by the toroidal-type continuously variable transmission 30 and, in the high speed running operation, the power is transmitted mainly by the planetary gear mechanism 31; and, a transmission ratio by the planetary gear mechanism 31 can be controlled by changing the transmission ratio of the toroidal-type continuously variable transmission 30.
For this purpose, the leading end portion (in FIG. 14, the right end portion) of an input shaft 11a, which penetrate through the central portion of the toroidal-type continuously variable transmission 30 and supports a pair of input side disks 2A, 2B on the two end portion thereof, is connected through a high speed clutch 35 to a transmission shaft 34 fixed to the central portion of a support plate 33 supporting a ring gear 32 which constitutes the planetary gear mechanism 31. By the way, of the pair of input side disks 2A, 2B, the input side disk 2B situated on the leading end side (in FIG. 14, on the right side) of the input shaft 11a, for example, similarly to the related-art structure shown in FIG. 13 which has been described above, is supported on the input shaft 11a in such a manner that it can be rotated synchronously with the input shaft 11a but can be substantially prevented against movement in the axial direction of the input shaft 11a. On the other hand, the input side disk 2A on the base end side (in FIG. 14, on the left side), for example, also similarly to the related-art structure shown in FIG. 13, is supported on the input shaft 11a in such a manner that it can be rotated synchronously with the input shaft 11a and can also be moved in the axial direction of the input shaft 11a. At any rate, the structure of the toroidal-type continuously variable transmission 30 is substantially similar to that of the related-art structure shown in FIG. 13 except for a pressing device 36 which will be described below.
Also, between the output side end portion (in FIG. 14, the right end portion) of a crankshaft 38 of an engine 37 serving as a drive source and the input side end portion (that is, the base end portion; in FIG. 14, the left end portion of the input shaft 11a, there are disposed a start clutch 39 and a pressing device 36 of an oil pressure type in series with each other in the power transmission direction. This pressing device 36 is capable of introducing a desired level of oil pressure which can generate a pressing force corresponding to the size of the power (torque) to be transmitted from the crankshaft 38 to the toroidal-type continuously variable transmission 30.
Also, an output shaft 40, which is used to take out power based on the rotation of the input shaft 11a, is disposed concentrically with the input shaft 11a. And, the planetary gear mechanism 31 is disposed on the periphery of this output shaft 40. A sun gear 41 constituting the planetary gear mechanism 31 is fixed to the input side end portion (in FIG. 14, the left end portion) of the output shaft 40. Therefore, the output shaft 40 is rotated according as the sun gear 41 is rotated. The ring gear 32 is supported on the periphery of the sun gear 41 in such a manner that it is concentric with the sun gear 41 and can be rotated. And, between the inner peripheral surface of the ring gear 32 and the outer peripheral surface of the sun gear 41, there are interposed a plurality of planetary gear sets 43, 43 each set consisting of a pair of planetary gears 42a, 42b. Each pair of planetary gears 42a, 42b are in meshing engagement with each other, the planetary gear 42a situated on the outside diameter side is in meshing engagement with the ring gear 32, and the planetary gear 42b on the inside diameter side is in meshing engagement with the sun gear 41. The thus structured planetary gear sets 43, 43 are respectively supported on one side surface (in FIG. 14, the left side surface) of a carrier 44 in such a manner that they can be rotated. Also, the carrier 44 is rotatably supported on the middle portion of the output shaft 40.
Also, the carrier 44 is connected to the pair of output side disks 4, 4, which constitute the toroidal-type continuously variable transmission 30, by a first power transmission mechanism 45 in such a manner that a rotational force can be transmitted between them. This first power transmission mechanism 45 comprises a transmission shaft 46 disposed in parallel to the input shaft 11a and output shaft 40, a sprocket 47a fixed to one end portion (in FIG. 14, the left end portion) of the transmission shaft 46, a sprocket 47b fixed to the output side disks 4, 4, a chain 48 interposed between the two sprockets 47a, 47b so as to extend between them, and first and second gears 49, 50 disposed such that they are respectively fixed to the other end (in FIG. 14, the right end) of the transmission shaft 46 and carrier 44 and also they are meshingly engaged with each other. Therefore, the carrier 4, 4, according to the rotational movements of the output side disks 4, 4, can be rotated in the opposite direction to these output side disks 4, 4 at the speed that corresponds to the number of teeth of the first and second gears 49, 50. By the way, this is based on the assumption that the pair of sprockets 47a, 47b are identical with each other in the number of teeth.
On the other hand, the input shaft 11a and ring gear 32 can be connected with each other in such a manner that the rotational force can be transmitted between them through the transmission shaft 34 disposed concentrically with the input shaft 11a. Between the transmission shaft 34 and input shaft 11a, there is interposed the high speed clutch 35 in series with these two shafts 34, 11a. Therefore, in the present structure, a second transmission shaft 53 is constituted by the transmission shaft 34. And, when the high speed clutch 35 is connected, the transmission shaft 34 can be rotated at the same speed and in the same direction as the input shaft 11a according as the input shaft 11a is rotated.
Also, the continuously variable transmission apparatus includes a clutch mechanism which constitutes mode switching means. This clutch mechanism comprises the above-mentioned high speed clutch 35, a low speed clutch 51 interposed between the outer peripheral edge portion of the carrier 44 and the axial-direction one end portion (in FIG. 14, the right end portion) of the ring gear 32, and a backing clutch 52 interposed between the ring gear 32 and a fixed part such as the housing (not shown) of the present continuously variable transmission apparatus. The clutches 35, 51 and 52 are structured in such a manner that, in case where any one of them is connected, the connection of the remaining two clutches is cut.
In the above structured continuously variable transmission apparatus, firstly, in the low speed running operation of a vehicle, the low speed clutch 51 is connected and, at the same time, the connection of the high speed clutch 35 and backing clutch 52 is cut. In this state, in case where the start clutch 39 is connected to thereby rotate the input shaft 11a, only the toroidal-type continuously variable transmission 30 transmits the power from the input shaft 11a to the output shaft 40. In the case of the low speed running operation, the transmission ratio between the two pairs of input side disks 2A, 2B and output side disks 4, 4 can be controlled similarly to the structure shown in FIG. 13 in which only the toroidal-type continuously variable transmission is used.
On the other hand, in the high speed running operation of a vehicle, the high speed clutch 35 is connected and, at the same time, the connection of the low speed clutch 51 and backing clutch 52 is cut. In this state, in case where the start clutch 39 is connected to thereby rotate the input shaft 11a, the power is transmitted from the input shaft 11a to the output shaft 40 by the transmission shaft 34 and planetary gear mechanism 31. That is, in case where the input shaft 11a is rotated in the above high speed running operation, the rotation of the input shaft 11a is transmitted to the ring gear 32 through the high speed clutch 35 and transmission shaft 34. And, the rotation of the ring gear 32 is transmitted to the sun gear 41 through the planetary gear sets 43, 43, thereby rotating the output shaft 40 to which the sun gear 41 is fixed. In this state, in case where the transmission ratio of the toroidal-type continuously variable transmission 30 is changed to thereby change the revolving speed (around the periphery of the sun gear 41) of the respective planetary gear sets 43, 43, the transmission ratio of the whole of the continuously variable transmission apparatus can be controlled.
That is, in the above-mentioned high speed running operation, the respective planetary gear sets 43, 43 are revolved around the periphery of the sun gear 41 in the same direction as the ring gear 32. And, the slower the revolving speed (around the periphery of the sun gear 41) of these planetary gear sets 43, 43 is, the faster the rotation speed of the output shaft 40 with the sun gear 41 fixed thereto is. For example, in case where the revolving speed (around the periphery of the sun gear 41) of these planetary gear sets 43, 43 is equal to the rotation speed of the ring gear 32 (both are angular speeds), the rotation speed of the ring gear 32 becomes equal to that of the output shaft 40. On the other hand, in case where the revolving speed (around the periphery of the sun gear 41) of these planetary gear sets 43, 43 is slower than the rotation speed of the ring gear 32, the rotation speed of the output shaft 40 becomes faster than that of the ring gear 32. Contrary to this, in case where the revolving speed (around the periphery of the sun gear 41) of the planetary gear sets 43, 43 is faster than the rotation speed of the ring gear 32, the rotation speed of the output shaft 40 becomes slower than that of the ring gear 32.
Therefore, in the high speed running operation, as the transmission ratio of the toroidal-type continuously variable transmission 30 is changed to the reducing side, the transmission ratio of the whole of the continuously variable transmission apparatus changes to the speed increasing side. In such high speed running operation state, to the toroidal-type continuously variable transmission 30, there is applied torque (assuming that torque applied in the low speed operation is positive torque, negative torque is applied) not from the input side disks 2A, 2B but from the output side disk 4. That is, in a state where the high speed clutch 35 is connected, torque transmitted from the engine 37 to the input shaft 11a is transmitted through the transmission shaft 34 to the ring gear 32 of the planetary gear mechanism 31. For this reason, there exists little torque which is transmitted from the input shaft 11a side to the respective input side disks 2A, 2B.
On the other hand, part of torque transmitted through the second power transmission device 53 to the ring gear 32 of the planetary gear mechanism 31 is transmitted from the planetary gear sets 43, 43 through the carrier 44 and first power transmission mechanism 45 to the respective output side disks 4, 4. In this manner, the torque to be applied to the toroidal-type continuously variable transmission 30 from the respective output side disks 4, 4 decreases as the transmission ratio of the toroidal-type continuously variable transmission 30 is changed to the reducing side so as to change the transmission ratio of the continuously variable transmission apparatus to the speed increasing side. As a result of this, in the high speed running operation, the torque to be input to the toroidal-type continuously variable transmission 30 can be reduced to thereby be able to enhance the durability of the composing parts of the toroidal-type continuously variable transmission 30.
Further, when rotating the output shaft 40 reversely so as to back the vehicle, the connection of the low speed and high speed clutches 51, 35 is cut and, at the same time, the backing clutch 52 is connected. Due to this, the ring gear 32 is fixed and the planetary gear sets 43, 43, while meshingly engaged with the ring gear 32 and sun gear 41, rotate around the periphery of the sun gear 41. And, the sun gear 41 and the output shaft 40, to which the sun gear 41 is fixed, are rotated in the opposite direction to the direction in the low speed running operation and high speed running operation.
By the way, the above-described continuously variable transmission apparatus is a transmission apparatus of a so called power split type which is arranged to reduce the torque that passes through the toroidal-type continuously variable transmission 30 in the high speed operation. In the case of the continuously variable transmission apparatus of this type, since the output shaft 40 cannot be stopped while the input shaft 11a remains rotating, there is necessary the start clutch 39. On the other hand, there is also disclosed in JP-A-11-63148 and British Patent Publication GB2 256 015 A, a continuously variable transmission apparatus of a so called geared neutral type structured such that, the specifications of the planetary gear mechanism and the combination of the planetary gear mechanism with the toroidal-type continuously variable transmission are modified, whereby the output shaft can be stopped while the input shaft remains rotating. In the case of the continuously variable transmission apparatus of a geared neutral type, when the output shaft is stopped or is rotated at a low speed, torque passing through the toroidal-type continuously variable transmission apparatus increases but, instead, the start clutch can be omitted.
Of the respective related-art transmission structures described above, the continuously variable transmission apparatus shown in FIG. 14 is advantageous in that transmission of torque is possible while securing durability. However, when taking it into consideration to transmit larger torque while securing sufficient durability, in the case of a simple combination of the related-art structures, there is a possibility that such combination is not be able to realize the above need sufficiently. That is, when taking it into consideration to realize a structure which is capable of transmission of larger torque using the structure shown in FIG. 14, there arises the need to transmit large power not only between the output portion of the start clutch 29 and input shaft 11a but also between the input shaft 11a and high speed clutch 35. However, in related art, there has not been known a practical structure which is capable of transmitting larger torque in these two parts. For example, in JP-A-11-303961, there is disclosed a structure in which the near-to-outer-surface-inside-diameter portion of the output side disk is concavely and convexly engaged with the end portion of a sleeve. However, since the diameter of the torque transmission part thereof is small, it is not always possible to transmit large torque.